We shall continue to use the experimental model of chronic renal insufficiency induced by partial nephrectomy in the rat for the study of the effects of chronic uremia on immune responses. The following lines of investigations are projected: (a) The attempt will be made to identify the cell population responsible for suppressor activity of uremic spleen cells. (b) The quantitative differences in the activity of control and uremic spleen and lymph node cells in mixed lymphocyte reaction will be investigated. The differences in the effects of uremia on the activity of the spleen population in graft-versus-host reaction, mixed lymphocyte reaction and its response to lectins will be analyzed. (c) The growth of an established 3-methylcholanthrene-induced tumor line will be compared in normal and uremic hosts. BIBLIOGRAPHIC REFERENCES: J. Raskova and A.B. Morrison, Suppressor activity of uremic spleen cells. Clin. Research 5, 585a, 1975. J. Raskova and A.B. Morrison, Graft-versus-host reactivity of uremic spleen cells: Increase in suppressor T cell activity. Fed. Proc., 1976.